An intraocular lens used by being implanted in the human eye with the goal of supplementing or substituting the function of the crystalline lens or the like of the human eye such as of a cataract patient or the like is known from the past. For example, the item disclosed in Japanese Unexamined Patent Publication No. JP-A-2005-021275 (Patent Document 1) is such an item, and has a structure including a roughly disc shaped optical part implanted within the eye and arranged on an optical path within the eyeball, and a plurality of support parts provided to the optical part and extending to the outer circumference side.
For this kind of intraocular lens, the support parts press against the equator part of the lens capsule from the inside and is projected and stretched in the radial direction so as to be positioned in order to stably hold the optical part at the center within the lens capsule. Therefore, with a single-piece intraocular lens that is a foldable type with the optical part and support part integrally formed with a bendably deformable soft material, which is currently the mainstream, it is necessary to make up for the material strength being low, and to ensure a positioning effect using the support part.
In light of that, with the conventional single-piece intraocular lens, it was necessary to make the width dimension and thickness dimension large to increase the strength of the support part. In addition, as is noted in Patent Document 1, it is preferable to use an elbow design for which at an inner circumference side edge part of the support part, the base end part has a narrow width so as to hollow out a small diameter arc, and which swells in convex form adjacent to the tip side. With this elbow design, by concentrating stress and distortion at the base end part of the support part which has a narrow width, it is said that it is possible to inhibit biasing or inclining of the optical part due to buckling deformation of the tip side of the support part, as well as to reduce deformation due to stress transmission to the optical part.
Meanwhile, with intraocular lenses, post-surgery secondary cataracts are a significant problem. These secondary cataracts are a result of crystalline lens epithelial cells wrapping around to the rear surface of the intraocular lens and propagating after surgery, and vision becomes significantly worse due to the posterior capsule of the intraocular lens back side becoming turbid.
With the goal of inhibiting such secondary cataracts, for example in PCT Japanese Translation Patent Publication JP-A-2005-507742 (Patent Document 2), it is also proposed to prevent the crystalline lens epithelial cells from wrapping around to the lens rear surface by pressing an outer circumference edge part of an optical part rear surface as a sharp edge cross section against the posterior capsule. However, there are problems such as that the edge cross section brings on thickening of the optical part outer circumference, and when the intraocular lens is inserted into the capsule, it is difficult to induce curve deformation of the lens so as to be sufficiently small and the like, and it was difficult to obtain a sufficient secondary cataract inhibitory effect simply by giving an edge cross section.
In particular, when investigated by the inventors of the present invention, with a single-piece intraocular lens made of a soft material whereby the width dimension or thickness dimension of the support part is made large, or an elbow design is used having at the inner circumference side edge part of the support part, the base end part with a narrow width part hollowed in a small diameter arc state or a part swelling in a convex shape, it was discovered that inhibiting the risk of occurrence of a secondary cataract tends to be even more difficult.